Geysers spewing sand and dust hundreds of feet into the air have been discovered on Mars, scientists say.
Images from a camera orbiting Mars have shown the 100mph jets of carbon dioxide erupt through ice at the planet's south pole, Arizona State University says.
The orbiting camera, called the Thermal Emission Imaging System (Themis), is on the Mars Odyssey probe.
The geyser debris leaves dark spots, fan-like markings and spider-shaped features on the ice cap.
The scientists said geysers erupted when sunlight warming the ice turned frozen carbon dioxide underground into high-pressure gas.
"If you were there, you'd be standing on a slab of carbon dioxide ice," said the university's Dr Phil Christensen.
"All around you, roaring jets of CO2 gas are throwing sand and dust a couple of hundred feet into the air."
Dr Christensen said the process was "unlike anything that occurs on Earth".
His team discovered the jets through examining more than 200 Themis visible and infrared images. The findings were published in the latest edition of the journal Nature.
An artist's impression shows the geysers erupting through ice